In the early hours of misery after one of the cruelest World Series defeats in franchise history, Red Sox fans unleashed torrents of frustration. At the umpires, for the obstruction rule. At Jarrod Saltalamacchia, for the wild throw to third. At manager John Farrell, for the questionable strategy.

Koji Uehara was upset, too — at himself, for surrendering the hit that fueled the Game 3 rally. But no one reading the Boston papers or watching local television the next day would have known it unless they were perusing his blog and could read Japanese.

“It’s my fault that I gave up the double,’’ Uehara wrote. “I’m very ashamed of myself that I threw such an easy ball even after being told by the bullpen coach to watch out for first pitches.’’

Uehara’s blog posts — translated for the Globe by Yohei Oka, a Harvard senior from Tokyo — provide a glimpse of Koji unfiltered. He dishes about himself, his teammates, his opponents, and, oh, the unforgiving nature of many in the Boston media, long a complaint of sports figures.

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Uehara, a 38-year-old veteran of five major league seasons after a 10-year career with the Yomiuri Giants, has been a revelation for the Sox on the mound and in the clubhouse.

Since Uehara became the closer by default in midseason, his performance has been unmatched in franchise history, and his personality generally has been nothing short of exuberant and inspirational.

It’s fair to say the Sox would not playing in the World Series without Uehara. In Sunday night’s Game 4, he became the first Japanese pitcher to record a World Series save. He also became the first pitcher to end a postseason game with a pickoff.

Uehara is eager to participate in another “champagne fight,’’ as his blog describes the celebrations that followed Boston’s first two playoff series.

Throughout it all, he has been refreshingly candid and humorous. His blog posts reflect similar whimsy, with a mixture of serious self-analysis and appreciation for his rarefied turn on the world stage, as well as thoughts about his teammates and opponents. Among the posts:

■ After David Ortiz homered twice to power the Sox to a 7-4 victory in Game 2 of the Division Series, Uehara observed, “The team seems to be in a good mood when Papi hits.’’

■ When the Sox eliminated the Rays, Uehara posted a photo of Ortiz hoisting him over his shoulder like a 100-pound bag of sugar.

‘Why do people write such negative articles when I’m trying to be optimistic and trying my best?’

“Am I that light? Or maybe it’s that Papi is too strong,’’ he wrote. “This color photo was in US newspapers the day after the game. This made me really happy.’’

■ In a 1-0 loss to Detroit in the opener of the ALCS, the Tigers threatened in the ninth when Uehara let runners reach second and third before he wriggled out of the jam. He bristled afterward about media references to his abysmal performance for the Rangers in the 2011 ALCS and the Lobaton homer.

“I’m always trying to pitch my best, but why do people keep bringing up the past?’’ he wrote. “An acquaintance told me that some stupid magazine has been writing stuff about me. I’m not saying for them to root for me, but it would be nice if they don’t write negative things about people doing their best.’’

■ With no margin for error, Uehara brilliantly recorded a four-out save in a 1-0 Sox victory in Game 3 against the Tigers.

“To be honest, I feel like throwing up. Stomach also hurts,’’ he wrote afterward. “We’ve come this far so I guess I have to whip my body a little bit more and keep pushing myself. After everything is finished, I’m going to drink a lot of beer.’’

He noted that Detroit fans taunted him by calling him “Ichiro’’ and “Daisuke.’’

■ Uehara logged a five-out save in Game 5 in Detroit to preserve a 4-3 win. The demands seemed to be taking a toll.

“Crap, I don’t know if my body is going to last ’til the end,’’ Uehara wrote. “There are so many ties and one-run moments when I have to pitch. It’s becoming much more physically and mentally exhausting.’’

■ With the pennant clinched in Game 6, Uehara was named the series MVP, and had his 7-year-old son, Kaz, by his side during the ceremony at Fenway Park.

“I’m scared that it’s all too good to be true,’’ he confided on his blog.

■ Uehara reacted to the controversial obstruction call in Game 3 of the World Series by calling for video reviews of every disputed play, not just home runs. He went on to express his shame for putting Cardinal Allen Craig on base in the first place, and his pride in finishing off Game 4 in historic fashion. But Uehara emphasized that he and the Sox face far more pressing matters.

“At this point, the game details don’t matter,’’ he wrote. “We just have to win!!’’

After Monday night’s game, Uehara permitted himself a moment of pride.

“ ‘First time in history’ has a very nice to ring to it,’’ he wrote. “There were a lot of those for me this year. I’m going to try to look them all up after the World Series.’’